The invention relates to replaceable cylinder elements on electrographic printing units used to print web or sheet material.
DE 37 05 477 C1 has disclosed a holding device for fitting a sleeve to a cylinder. In order to fit a sleeve through an opening in a printing-unit side wall, on the outside of the other printing-unit side wall of the cylinder, on the lengthened shaft journals of the cylinder, an eccentrically mounted auxiliary shaft mounted above the cylinder and arranged transversely is positioned in a gearbox. By setting nuts, the auxiliary shaft and thus the shaft journal of the cylinder can be adjusted and fixed horizontally. In this arrangement, a sleeve is pushed laterally through an opening in the printing-unit side wall onto the solid printing-unit cylinder of a printing unit in a rotary printing machine.
DE 40 36 387 A1 and DE 40 36 388 A1 each reveal mountings for printing-unit cylinders in rotary printing machines. The first laid-open specification discloses a mounting for a printing-unit cylinder in a web-fed rotary printing machine, having a cover which can be interchanged and, for this purpose, can be drawn axially off the cylinder. An auxiliary device which supports the cylinder on one side when the cover is being changed is intended to lock said cylinder by enclosing it but not to impair and not to contact it during printing operation. For this purpose, according to DE 40 36 387 A1, outside and/or inside the machine side wall which continues to bear the journal when the cover is being changed, a roller with a concave outer face which supports the cylinder can be brought into contact with the journal, being mounted on a lever that is mounted in the machine frame and can be pivoted over in the longitudinal direction of the journal.
DE 40 36 388 A1, constitutes an alternative solution, outside and/or inside the machine side wall that bears the journal of the cylinder, it being possible for a lever which supports the cylinder to be brought into contact in each case with the journal, and for said lever to be rotatably mounted in the frame, has an eccentric which is located beside the journal and perpendicular to the supporting face and, by means of a four-bar linkage, is connected to a further eccentric mounted in the frame on the other side of the journal. This solution, which entails a quite complicated mechanism, relates to printing units of web-fed rotary printing machines, with which solid cylinders are supported in the printing unit during a sleeve change.
DE 40 36 390 A1 and DE 40 36 391 A1 each relate to mountings for printing-unit cylinders in web-fed rotary printing machines.
DE 40 36 390 A1 reveals an auxiliary device which supports the cylinder of a web-fed rotary printing machine on one side when a cylinder cover is being changed, and locks the cylinder but does not contact it during printing operation. For this purpose, a centering piece which is mounted centrally in relation to the journal of the cylinder, which is mounted in the machine side wall and projects from the latter, is arranged in the machine frame or can be pushed into the journal.
DE 40 36 391 A1 likewise relates to a holding device for a printing-unit cylinder during the time at which a cover is being changed on the latter. According to the solution from DE 40 36 391 A1, outside and/or inside the machine side wall which bears the journal of the cylinder, in each case a carriage which is arranged such that it can be displaced in the frame, supports the journal and partially encloses it in a recess, can be brought into contact with the journal by an eccentric.
U.S. Pat. No. 4,119,032 likewise discloses a holding device for a cylinder which has its cover changed when it is installed in the printing unit of a printing machine. For this purpose, one journal of the complete cylinder, which is mounted in the side walls of the printing machine, can be exposed by removing part of the side wall, while the other cylinder journal provided on the drive side is enclosed by a yoke, so that the cylinder remaining in the printing unit is protected against tilting, and the cover of the cylinder can be replaced.
EP 0 575 739 B2 relates to a device for supporting a cylinder in a rotary printing machine having a frame of side walls arranged spaced apart from each other. Provided therein is a printing cylinder having a supporting element for supporting the ends of the printing cylinder in the side walls. The supporting element can be removed from one end of the printing cylinder, a counterweight mechanism being provided which has a rotary arm that can be adjusted in position and which, in a supporting position, exerts force on the other end of the printing cylinder, in order to support the latter in the frame when the supporting element is being removed. A hinged piece for moving the rotary arm into the position in which it supports the cylinder, and for holding the rotary arm in this position against the weight of the printing cylinder, has an end position for its mobility for adjusting the rotary arm. By the end position, a surprising or sudden pressure drop in the holding system can be prevented, and the cylinder can be held in its position in the printing unit of the rotary system even in the event of a pressure drop in the hydraulic system of the holding apparatus.
U.S. Pat. No. 5,215,013 relates to a cylinder which is accommodated in a printing unit of a web-processing rotary printing machine and onto which a sleeve-like transfer sleeve can be pushed. For this purpose, before being pushed onto the cover of the cylinder, which is located in the printing machine and supported on one side, the sleeve is widened by pressurized air, so that the sleeve can be pushed laterally onto the cover. The air flowing out laterally from the air cushion during this process causes high-frequency noise, which is damped by a damping ring let into the sleeve to be pushed on.
U.S. Pat. No. 5,649,267 discloses a method of arranging a drum, it being possible for the drum to be used in a printing unit. A toner image can be arranged on the circumferential surface of the drum, which is used as an endless rotating surface. The drum includes a hollow cylinder with an opening at each end and a surface onto which the toner image can be applied. A supporting face, which contains an opening in its interior, is cooled down before it is inserted into the drum surface at its ends, and is thus shrunk into the open ends of the outer face of the drum. When the previously cooled, disk-like elements are heated, these expand and thus produce a press fit between the outer face and the ends. In addition, openings, in which a carrier supporting the drum can be accommodated, are provided in the ends. In the case of the solution according to U.S. Pat. No. 5,649,267 there is the disadvantage that, in order to renew the functional layer on the outer face of the cylinder, the complete arrangement has to be replaced, since the ends of the drum arrangement are in each case shrunk into the arrangement forming the outer face. Cooling within the machine in order to break down the ends around the drum arrangement in the machine, is extremely complex and cumbersome.
In the case of cylinder arrangements with photoelectric functional surfaces, wear which sets in, for example as the result of the removal of particles from the surface, necessarily occurs over the surface life, depending on the stress on the photoelectric layer, and constitutes a technical problem.
In view of the solutions disclosed from the prior art, which primarily relate to supporting solid cylinders on one side in web-fed rotary printing machines, and the solution disclosed by U.S. Pat. No. 5,649,267, the invention is based on the object of simplifying the replacement of a functional layer, for example a photoelectric layer, on a cylinder of a printing unit, and of carrying out such replacement within the printing unit with extremely low outlay.
According to the invention, in the case of a cylinder with a functional layer and with a supporting body which passes through the cylinder and on which there are provided two ends which support a sleeve that accommodates the functional layer, the supporting body being supported in supporting elements on the frame side, the sleeve that accommodates the functional layer can be centered in relation to the axis of rotation by centering faces formed at the ends supporting said sleeve, it being possible for one end of the cylinder to be exposed at a supporting element. The advantages which are associated with the solution proposed according to the invention reside primarily in the fact that a cylinder arrangement is such that following the exposure of an opening in one side wall supporting the cylinder arrangement, it can be removed laterally from the printing unit. After one end with centering faces has been detached, from the supporting body, the worn outer surface can be replaced, for example, by a reworked or even a new photoelectric functional layer, it being possible for the ends that accommodate the centering faces and the supporting body that passes through the cylinder arrangement, together with all the rolling-contact bearings accommodated thereon, to be reused. The solution according to the invention is primarily associated with the economic advantage that the entire cylinder does not have to be replaced, since the centering faces form detachable connections between the ends and the cylinder sleeve that bears the functional surfaces in contrast to press fits which are formed by shrunk connections, which can be detached only with difficulty.
In a further refinement of the idea on which the invention is based, the ends which are accommodated on the supporting body, that is to say an axle/shaft, are provided with circumferential centering faces. The circumferential centering faces at the ends can have a specific geometry, it being possible for the cylinder sleeve that accommodates the functional layer to be provided at its ends with a chamfer which is complementary to the chamfer on the centering faces of the ends which accommodate the sleeve. In an implementation which is advantageous and particularly simple in production terms, the centering faces at the end faces can be formed as chamfers.
In an advantageous refinement of the idea on which the invention is based, one of the ends can be positioned on the supporting body in relation to the other end of the supporting body. By fixing the axial position of one end and an end which can be displaced in relative terms with respect to this fixedly positioned end, inaccuracies caused by production can be compensated for without difficulty, and in addition an eccentricity can be set by suitable selection of the centering faces. The relative adjustability of the positionable end in relation to the end which is accommodated in a stationary manner on the supporting body, permit both the rotation of the positionable end in the circumferential direction on the supporting body and its axial displaceability relative to the other end.
In an advantageous refinement of the idea on which the invention is based, the positionable end is provided with a clamping device. For this purpose, said clamping device can contain a pressure element which can be prestressed axially by a slotted nut and which, by the slotted nut, transmits the axial force acting on said pressure element, by radial deformation, onto a radially deformable sleeve which is accommodated between the relatively positionable end and the supporting body.
In one alternate embodiment, the positionable end on the supporting body can be configured as a sleeve-like element that engages over the supporting body and a bearing journal provided on the latter. The end configured as a sleeve-like element can in turn function as a bearing element for the supporting body. For this purpose, in a region of the sleeve-like end which is located closest to the frame wall, a bearing element can be provided on the outer circumference of this sleeve-like element, with which bearing element the supporting body can be mounted in the frame wall.
In order to expose one end of the cylinder arrangement according to the invention proposed, one end of the cylinder arrangement can be exposed by removing a fixing element that accommodates the bearing point of the cylinder arrangement from the frame side wall.
The solution according to the invention can preferably be used in a printing mechanism of a printing unit which is used for small editions with rapidly changing subjects, such as those printing units to whose cylinder outer surfaces toner images are applied, for example to photoelectric functional layers, which are subject to wear as a result of the principle.